Pentax DSLR (K-30,K-5,K-5 ii) for sports?

It's a shitty lens on your D7000, rather than a camera itself. For sports you need fast lens, in terms of both - aperture (f/2.8) and AF speed. Pentax AF system (even SAFOX X in K-5II) is slightly inferior than comparable cameras from Canon and Nikon in terms of focus tracking, I guess mostly because it has less AF points. K-5II/IIs has much better AF-C mode than any Pentax camera before, but still not as good as 7D/D300s or even D7000 (not to mention real sports beasts from both companies) and also Pentax has no really fast lens with a ring type AF motor which could help a lot.

It doesn't mean you can't use Pentax cameras for sports - you can and you can find a lot of good sports pictures made with them, but it combines both photographer skills and at least some more suitable lens than all around amateur zoom like your 18-200.